This invention relates to speech processors, and more particularly to analog speech processors which are implemented with charge coupled devices (CCDs). The CCD speech processors have several applications. They may be used, for example, in speech recognition systems. Such a system may function to recognize the voice of particular speakers, and as such may be used as a security device. As another example, a speech recognition system may be used to first recognize spoken words, and then to translate them into digitally encoded form which can be operated on by a machine. Speech processors are also used as data compressors. It is well known that speech waveforms contain much redundant information. A speech processor may be used to eliminate this redundancy, and thereby achieve a significant bandwidth reduction from the original speech signals.
Several approaches have been used in the past to physically construct speech processors. Many of these methods are described in an article by White, in the May 1976 issue of "Computer" at pp. 40-52. One of the most important of these methods is called linear predictive coding (LPC). This method is described in an article by J. Makhoul entitled "Spectral Analysis of Speech by Linear Prediction", in the 1973 IEEE Transactions on Audio Electroacoustics, Vol. AU-21, at pp. 140-148. Basically, linear predictive coding is a digital method of analyzing speech. One problem, however, with this approach is that it requires some complex mathematical operations to be performed, which are expensive to implement with today's digital technology. As such, the method becomes impractical for many low cost applications.
Accordingly, it is one object of this invention to provide relatively low cost CCD speech processor.
Another objective of the invention is to provide a CCD speech processor which operates directly on analog signals representing the speech waveforms.